//  https://www.luogu.com.cn/problem/P1002

#include<iostream>
using namespace std;

int n, m, x, y;
const int N = 25;
int arr[N][N];
long long dp[N][N];
int dx[] = { 1,2,2,1,-1,-2,-2,-1 };
int dy[] = { 2,1,-1,-2,-2,-1,1,2 };

int main()
{
    cin >> n >> m >> x >> y;
    n++, m++, x++, y++;
    arr[x][y] = 1;
    for (int i = 0;i < 8;i++)
    {
        int a = x + dx[i], b = y + dy[i];
        arr[a][b] = 1;
    }

    dp[0][1] = 1;
    for (int i = 1;i <= n;i++)
    {
        for (int j = 1;j <= m;j++)
        {
            if (arr[i][j] == 0)
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
        }
    }
    cout << dp[n][m] << endl;
    return 0;
}